Change engine oil annually even if it's pristine?

[pesarsten]

I have been told from a variety of well informed mechanics that the oil is ideally changed before a winter storage. While the oil may be fine for lubrication purposes, it becomes acidic and not ideal for extended storage.

As a rule, my oil is changed every fall during winter prep, and at about 100 hrs of use in the spring. I consider it cheap precautions for an expensive engine.

[rslifkin]

Acidity becomes a problem as the oil gets used up. But if it's still early in its usage life, it should have more than enough ability to buffer acids and shouldn't present a concern. That said, I'm generally fairly close to the 100 hour oil change interval for my engines at the end of the season, so I just change the oil before winterizing.

[Cadence]

Originally Posted by OrangeCrush

I had a baby this year and didn't use my boat nearly as much as usual. I put less than 20 engine hours on it and the oil is in "like new" condition, light amber with no darkening at all. (It's a Yanmar 4JH5E with 900 hours total and I use Delo Heavy Duty Diesel oil).

I'm in the habit of changing it annually or sometimes twice annually if it's dirty. It just seems unnecessary this year and I'd love to skip a step. It seems like the conventional wisdom is to change it every 250 hours or every year, whichever comes first. But if the engine oil is truly pristine is there any harm in skipping a year or is time really a factor?

Why not? It costs little or nothing.

[chasmains]

A significant problem over time is condensation. You may not know it, but engines “breathe” all the time. The cycle is repeated continuously. If you have had a warm up, then cooling draws in lots of outside air which is laden with varying levels of humidity based on the day and time you shut down. Some condensation will occur during engine cooldown. But the next day and all days that follow will make the engine breathe repeatedly as local atmospheric pressure, humidity and temperature change over each day’s cycles. So an engine warms up a little during the typical day. The air already inside breathes out. Later, the engine cools in the overnight and breathes in, bringing whatever humidity there may be locally. This will condense out a little and move to areas inside the engine that have low water vapor partial pressure and some will get into the oil. Not saying a lot of water vapor but some. And it happens every day. On high atmospheric pressure days and nights more breathing in happens. So long term, moisture content builds up slowly.
Many non-synthetic oils have some chemicals that turn to acids. These can be the corroding acids. Not all are. But Nitrogen oxides can become nitric acid, and sulfur oxide compounds can form sulfuric acid, both love steel and bearings. Low sulfur diesel fuel helps but doesn’t stop it. Just like your car engine, boat motors need to be run occasionally. And all the way to full operating temperatures. If not done, the captured water is not “boiled” out of the oil. Crank cases are a little better. They are often sealed and don’t heat up to engine temps mostly. But the still need attention.

[chasmains]

By crank cases I mean gear boxes. Please excuse the error.

[captlloyd]

“ less than 20 hours”, don’t bother, you would be wasting money. I don’t care how cheap an oil change is, wasting money is wasting money. Your engine will be fine. Change it once or twice next year.

[Seymore]

Yanmar says to change the oil every year because oil breaks down over time. Ask a Yanmar dealer or mechanic.

In CF, Boatman61 has posted his experiences with bad oil but I can't find his post.

[Simi 60]

Originally Posted by Seymore

Yanmar says to change the oil every year because oil breaks down over time. Ask a Yanmar dealer or mechanic.

In CF, Boatman61 has posted his experiences with bad oil but I can't find his post.

They would also tell you to use Yanmar oil and filters

In other news a butcher says today's a great day to buy steak.

[MatthLE]

Modern oil includes the ability to hold suspended and isolated many contaminants including moisture. Also like any oil it does oxidize and become acidic. Time is a factor. Ask the gents that make the oil. They are far more ontop of the current formulation than us. Otherwise when in doubt punt, the cost of being wrong far outweighs the savings in retaining possession.

Respectfully

[Methersgate]

Originally Posted by OrangeCrush

I had a baby this year and didn't use my boat nearly as much as usual. I put less than 20 engine hours on it and the oil is in "like new" condition, light amber with no darkening at all. (It's a Yanmar 4JH5E with 900 hours total and I use Delo Heavy Duty Diesel oil).

I'm in the habit of changing it annually or sometimes twice annually if it's dirty. It just seems unnecessary this year and I'd love to skip a step. It seems like the conventional wisdom is to change it every 250 hours or every year, whichever comes first. But if the engine oil is truly pristine is there any harm in skipping a year or is time really a factor?

Snap! I have the same engine, but 3,565 hours. It’s just done 5 hours since the last oil change and I think I can leave it over the winter.

[Grattaway]

Congrats on new baby - hopefully another boating buddy
My experience is that you can leave the oil change this year - others here say just do it anyway but I am sure with a new baby you have enough to do already

There are 10's of thousands of diesel engines that will have been in worse environmental conditions that yours where oil changes will have been longer than 12 months with negligible impact. So unless some obvious reason to change oil dont stress, baby comes first, engine will be fine.

[parkstone bay]

I had the same problem last year: my opinion - FWIW - with a normally aspirated engine, with only 20 hours since last oil and filter change, is yes, you can leave it. BUT, make sure she's turned over once or twice during the winter, to prevent brinelling (spot hardening) of the bearings - AND - babies or no babies, do the oil change next year for sure. As has been mentioned by several posters, used engine oil tends to become acidic with the combustion products, so change the oil before the winter lay-up.

[The Way]

I'm following this thread with great interest, since I rarely go out sailing but want to preserve my engine.

I can't help remembering several times seeing people buy and install diesel engines that had been sitting in a shed for years. These people didn't seem to think engines deteriorated over time just by sitting there, like potato salad :-)

How come engines that have been sitting for years have any cash value, if changing oil so often is required?

Thanks for any advice,
Jack

[strojin]

......synthetic oil lasts longer than conventional oil. If you send a small sample of your used oil for analysis it will tell you how much life is left in the oil. The additives are important too and that is where the annual oil change is the least recommended by most mechanics.

[timb7734]

I owned a trucking company for 49 years so have a bit of experience maintaining diesels. Modern engines and the oils specified do not deteriorate sitting around.

There are those with older engines using straight viscosity oils who will argue that oils are cheap compared to overhauls, but seldom will over maintaining prevent engine failure.


We ran trucks about 500 hours between changes with sampling and these engines were still fully rated at 500,000 miles when they were traded. That’s the equivalent of over 10,000 hours.


IMHO just follow manufacturer recommendations as to hours to oil changes if you are using a multi viscosity oil rated for your engine. Their additive packages don’t go bad.